Electron discharge tube



June 5- ,J. o. HARRIES 2,401,637

ELECTRON DIS CHARGE TUBE Filed Sept. 4, 1941 4 Sheets-Sheet 1 I 1 ll I\12 Fig.1. I

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Filed Sept. 4, 1941 INVENTOE June 4, 1946. J. H. b. HARRIES V240L637ELECTRON DISCHARGE TUBE I 4 Sheets-Sheet 4 //YVENTO $1; 172.4 a

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Patented June 4, 1946 UNITED. STATES PATENT OFFICE ELECTRON DISCHARGETUBE John Henry Owen Harries, Clapham Park, London S. W. 4, EnglandApplication September 4 1941, Serial No. 409,588

' In GreatBritain September 5, 1940 9 Claims. 1

that circuits for use with a tube for both input and output purposes ingeneral consist of an enclosed metallic structure or casing such as thatof the well known shielded concentric quarter wave line. The radiationlosses insuch a transmission line circuit become very considerable ifthe continuity of its outer conductor or shield is broken. It is noteasy: to devise a construction for an electron discharge tube such as adeflection valve which enables an electron beam or stream inside theevacuated envelope of the tube to be deflected or modulated by the fieldof an input circuit, and which 'enablessuch' an electronbeam to giveenergy to an output circuit which is necessarily external to the tube,while at the same time maintaining a low loss in theinput and outputcircuits. This difiiculty is aggravated by the necessity of providingtuning. adjustmentmechanism for the circuits. Possibly, however; thegreatest complication arises because, in addition, some means has to be.employed to remove excess-heat during operation from the assembly of thedischarge tube and its circuits. This is particularly necessary in thecase of tubes provided with massive copper electrodes sealed into glassenvelopes. Suchv electrodes are often necessary in discharge tubesoperating with ultra high frequencies in order to provide a low lossconnection in the external circuit connected to the electrodes of thetube; such copper electrodes must not be allowed to rise to a point atwhich the joints between the copper and glass may be damaged or gasevolved from the internal parts of the tube. Water cooling of theappropriate parts is, of course, extremely effective but is mostinconvenient and expensive.

The chief object of the invention is to providea methodof constructionfor a valve andits circuits to operate at ultra high frequencies andwhich are electrically efiicient and are readily and efliciently cooledduring operation.

According to the present invention, an electron discharge tube ismounted on a supporting platform and a, casing forming part of ashielded circuit connected to the discharge tube, such as the outputcircuit, or forming. part of the input and output circuits, is; alsocarried by the said The temperature of- .2 platform and surrounds thetube, while means are provided for drawing a stream of air through thecasing to serve as a cooling mediumior parts of the tube which duringoperation would otherwise become overheated. The platform may constitutea partition in the said casing which it divides electrically andmechanically into two parts which actually form parts of the input andoutput circuits of the discharge tube. The supporting platform may alsoserve for connecting an electrode in. the discharge-tube to its externalcircuit, and in fact, an electrode constituted by a transverse platesealed to the envelope of the discharge tube and extending outside theenvelope. In some cases, for example, in the dischargetube set. forth inpatent application Serial No. 409,585, filed September 4, 1941, such anelectrode has to be maintained at a different direct potential from theexternal circuit which may be at a. higher potential, and then theplatform, while mechanically supporting the casing,

may be electrically connected to it through the dielectric of acondenser,

This arrangement enables the air stream provided for cooling purposes tobe directed on to the said transverse plate electrode, and an: anode oroutputelectrode may alsobe extended to the outside of the envelope andcooled by direct contact with. the air stream. Generally speaking;

the air stream may be directed into the neighbourhood of any parts whichrequire especially effective cooling. In particular, when the easing isdivided into two parts by the partition, streams of air' maybe drawnthrough the two parts and at one end directed towards an outputelectrode, and at the other end towards lead-in conductors of otherelectrodes. The transverse plate electrode ma be furnished with externalheat radiating surfaces or fins which are cooled by the stream of air. a

As regards the tuning mechanisms, these may be mounted on those parts ofthe casing which form part of the external circuits and may be arrangedfor the adjustment of the dimensions of' the casing necessary for tuningthe circuits to the required frequencies. For example, at least one endof the casing may consist of two telescoping members which maybeextended or contracted by the tuning mechanism so that for tun'-' ingpurposes the effective length of the end of the casing is changed.

In order that the invention may be clearly understood and readilycarried into effect, some forms of construction in accordance therewithwill now be described by way of example with reference to theaccompanying drawings, in which:

Figure 1 is a central section showing the mounting of the tube within acasing forming part of the. output circuit;

Figure 3 is a longitudinal section showing another type of tube in whichthe casing forms part of the input and output circuits;

Figure 4 is a longitudinal section seen at right-.

angles to Figure 3 of the end of the enclosing casing containing thetuning arrangements for the input circuit;

Figure 5 is a general diagrammatic View showing two suchtubes in theircasings mounted on a deck forming the top of a cabinet; while Figure 6is a general View showing the mountingof a tube as shown in Figure 1.

Referring to Figures 1 and 2, the anode end of a tube is shown of theconstruction set forth in patent application Serial No. 409,585, filedSeptember 4, 1941, or in Figures 1 to 11 of the draw ings accompanyingthe specification of patentapplication Serial No. 409,589, filedSeptember 4, 1941. The upper part of the envelope E is shown with theoutput target or anode T fused into a re-ntrant seal, while thesub-anode SA is sealed to the two parts of the glass envelope E. Thetube is mounted by bedding the sub-anode SA on to a seating of a brassring'3ll with a thin silver ring 3| interposed to make good contact. Thesub-anode SA is pressed on to the seating by three equally s aced screws32 screwed radially into the ring 30, and formed with conicalpointswhich press the sub-anode SA on to the seating,

as shown in detail inFi ure 2. A voltage of 1500 volts for the sub-anodeis applied to a ring 38a which is in metallic contact with the ring 30so that the rings 30. 30a constitute a metal platform support for thedischarge tube. The terminal of the target T consists of a rod I2 whichis actually'tubular as shown. and is perforated near its lower end forcooling purposes. For this purpose. air is forced into the upnerend ofthe rod I2 and passes out through the perforations at the bottom intocontact with the tar et T and into the inside of a telescoping casing33, 3! which form's'part of the output circuit. .It passes out of thiscasing through vent holes 40a in the upper wall 45 of the casing. Therod I2 is screwed into the target T so that both it and the discharetube, which is a deflection valve. are fixed relatively to the'brassring 30. The part 33 of the casing which is of sheet metal and open atthe top. is soldered 'to another brass ring 34 secured by screws 35 to athird brass ring 36. A s eet metal cap 31, which also has its lower endsplit at 38, telesco es into the part 33 and has a tubular sleeve 39soldered into the end wall 49. The sleeve 39 is capable of sliding onthe rod l2 so that the latter, the sleeve 39, the end wallMJ, the cap31. the sheet metal casing 33, and the brass rings 34 and 3B, are allsubjected to the voltage of the target T, which in this example is 2500volts. Therefore, these parts have to be insulated from thread engagedby "a threaded sleeve 5i fixed by' connected. This assembly, as a whole,will be recognised as a concentric line type of tuned circuit. To reducelosses while enabling sufficient mechanical strength to be maintained,the parts 33, 31, 40, and the rings 30, 30a, 34 and 36, should be madeof brass andbe silver-plated. Good contact surfaces must be maintained.

'It is arranged that the metal cap 31 can slide for tuning purposesrelatively to the sheet metal casing 33 and the brass rings which arefixed to the sub-anode SA, and to enable this to be done, a sleeve 45 issecured by grub screws 48 to the sleeve .39 and is provided with aright-handed screw-thread 41 on its outer surface This screw threadengages an internal right-handed thread in a nut 48 fixed within anebon'it'e adjusting disc 49. On the other sideof this disc the'le'ls anut 50'which has an internal left-handed screw grub screws 52 to theupper part of the rod l2.

Now if the ebonite disc 49 is rotated so as to'cau'se" the nut 58 toride up on the screw-thread of the sleeve 5|, owing to the fact that thesleeves 5! and 45 have threads of opposite hand, the sleeve] 45 will bedrawn upwards into the nut 48 at doublethe rate if the pitches of thetwo screw-threads are the same. Thus, the sleeve 39, a d the sheet metalcap 31 are drawn up relatively to the metal casing 33. Similarly, if thedisc 49 is rotated in the opposite direction, the cap 31 is forced downinto the casing 33, and in this way tuning of'the concentric. conductorsl2 and 33, 37is efiected. The loop [5 is a pick-up loop connectedtoconductor 53 for connection to a di-pole transmitting aerial. The loop54 is a tuning loop connected directly to a small lamp 55 which, by its;

brilliance, indicates the tuning point.

In Figures 3 to 5, the mounting of tubes is shovm. the envelope of eachof which has a central copper section between two end sections of glass,as shown in Figures 12 to 21 of the draw ings accompanying patentapplication Serial No] 409,589 referred to above. The output circuitarrangements making use of a concentric'conductor system shown in Figure3, includesa sheet metal casing 33 with a cap 31 and endwall 43, to thelatter of which is secured the'slee've 39 which is caused to slide overthe tubular conductor l2 which is screwed into the target'elec trode T.It will be noticed that in this case the target electrode is not sealedinto a re-entrant' the brass ring 33a which, as already mentioned,

is at the sub-anode voltage of 1500 volts. For this purpose, a sheet ofmica 4| about0.01 inch in thickness is interposed between-the brassrings 36a and 36. but these'rings are mechanically seseal and is moreaccessible to the cooling .air which enters through apertures H0 andleaves through the outlet pipeslll. j 1

The tube is secured in this case to a deck- 83, and for this purpose,while the sub-anode SA is'bedded on to a plate 30 which again forms ametal platform support separated from the parts metallically'connectedto the target electrode T by a sheet of mica 4| forming the"clielectric of a condenser as described above'with reference toFiguresl and 2, the central copper part E of the envelope of thedischarge tube has a system of cooling fin forced on to it. This .faceof the ring 84 have a slight taper. The

surfaces are cleaned and the ring 84 pushed on to the'tube 'E' to makegood thermal con-i tact with it, At the lower outer edge of the fins 85,there is an outwardly-extending ring :or.

flange 86 which is secured by screws B'I'to the"- deck 83.

The tuned input circuit also consists of a shielded two-wire adjustabletransmission line. Its shielded casing provides a means of applying aircooling and acts as a support for the lead-in wires. Thus, the ring 84is extended downwards at 88 beyond the fins 85, and this downward ex- Itension receives the cylindrical shield 89 of the input circuit whichconsists of metal tubing fixed in position by screws 90. The lead-inconductors d d tothe parts D D of the deflection cylinder are connectedby short lengths of braided flexible conductor W to a pair of'Lecherwires 92. For tuning purposes a piston orplunger 93 is provided whichcan slide in the casing 88 and forms the adjustable bridge-piece betweenthe Lecher wires 92. In order to facilitate assembly, the casing 83 hasa flanged joint at 94. The piston 93 is adjusted by a handle 95 on thelower end of a screw-threaded rod 95 which, as seen in Figure 5, istaken out through insulating bushings 91 mounted in the lower wall 98 ofthe casing or cabinet 99' which encloses the pair of tubes shown in thatfigure. The rod 96 screws in a nut Hi6 forming part of the bottom wallof the casing 89; and the rod 96 extends through the wall of the piston93 in which it can turn but is prevented from sliding relatively to thepiston by a pair of nuts Ill-I pinned to it. The input supply is broughtto it by a pair of shielded conductors I82 which feed into a loop Ill-'3carried inthe wall of the piston 93, by an insulated thimble I04. Allhigh frequency tuning conductors may be of brass and should besilverplated to reduce losses.

Cooling is partially eiTected by a relatively slow current of airindicated by the arrows I85, which flows in radially between the fins 85and through the annular hole I86 in the deck 83, as seen in Figure 3. Inaddition to this, the lower seals for the lead-in wires of the valve andthe target seal are cooled by higher speed air currents. It has alreadybeenmentioned that for the latter air is drawn in as indicated by thearrows Hil in the outlet" circuit casing 33 and is taken away throughtwo outlet pipes I'Ii which may be of glass and pass through the endwall 40 of the cap 31. For the lower seals the air'passes in throughinclined glass tubes Iill which are optional but which, when provided,prevent this air from coming into contact with the fins 85 and thusbecoming heated. The high speed air current follows the arrows I93 intocontact with the lower seals and is; taken away laterally through thecasing 89 by way of an outlet pipe I89.

The arrangement is capable of modification by" altering the tubes andaperture so as to direct the air to desired parts of the assembly. Theoutlet pipes may be of any material not having high electrical losses. Aby-pass condenser is shown as formed of a copper band I I2 encirclingthe input casing 89' and separated. from it by a sleeve of mica H3; Thelead-in conductors may be by-passed to the case with respect to ultrahigh frequency currents, by the method illustrated, by way of example,in the drawings by the conductor. 8 which is brought out through abushing H4 in the side of the casing 89 and is connected by a wire. I IEto the copper band II2 of the condenser. A piece of mica (not shown) maybe'used to keep dust out of the condenser 36, 38 and the entering airmay be cleaned or filtered in any convenient Way.

In the complete arrangement shown in Figure 5, two tubes enclosed incasings, as shown in Figures 3 and 4, are mounted on a deck 83 which 6forms the top of a cabinet 95. The lower outlet pipes I09 from thetubular casings 89 and the upper outlet pipes II I are both brought intoan outlet manifold H 6 from which the heated. air

I is" withdrawn by a fan. at H 1" driven. by at small Figure 1. Again,it is mounted on a deck 83 'forming' the top of the cabinet 99', but inthis case the tube is inverted with respect to Figure 1' so that the endcontaining the cathode is uppermost and the end containing the outputtarget is directed downwardly. The telescoping casing 33, 3?: with theoutlet conductorsit! and tuningmec'hanisrn 55 are shown as in. Figure 1,and indeed the arrangementonly differs from that figure in details; forexample, the tubular rod I2 and the sleeve 39 are lengthened so that thetuning: handle d9 can be located outside the cabinet: 99.- The sleeve 39in fact passes. through the bottom of the cabinet by way of aninsulating bushing 39a; The discharge tube itself is fitted with fins 85similar to those shown in Figure 3, but they are in contact with thecondenser plate 38- in which the sub-anode SA is clamped. The cooling 1of the target end of the tube is efiected inthiscase by allowing air toenter the casing 33; 31 through inlet pipes I21I as shown by arrowsI-22. These pipes I2 I are brought through the deck Ei3-an d communicatewith the inside of the casing 83 The upper end of the discharge tubewith the leadin wires for the otherelectrodes is, as shownat the top ofFigure 6, located in the surrounding air. The tubular rod I2 isconnected at its lower end toa tube I35 outside thecabinet 99 andconnectedto the fan II 5 driven by the electric motor M8 by aninternalpipe I23. Thus, the tan I-ti' draws in air as shown. by the arrows I2 2,which flows into the casing 33, 3-1 in contact with the target throughthe tubular conductor rod I2 by way of the tube H6 and pipe I23, and outthrough the fan III. In order to cool the outside of the casing 33, 3-1,air is drawn in through the deck 83 around the tube itself", as shown bythe arrows I24. This relatively slow stream of air is drawn out from thecabinet 99 by the fan I I9 driven bythe electric motor I28.

I claim:

1. Anelectron discharge tube instailation comprising a metal platformsupport, an. electron discharge tube having a plurality of electrodesincluding an. electrode extending outside the envelope of said tubewhere same is in contact with support, a layer of (ii-electric materialin contact with said platform support, a metal plate spaced from saidplatform by said (ii-electric material, a metallic casing, enclosingatleast part of. said discharge tube and secured to said metal plate andelectrically connected to a further electrode of said tube, and formedwith. inlet and;

outlet apertures for cooling fluid and means con prising an electrondischarge tube having-an electrode extending outside the envelope ofsaid tube, a metal partition in contact with and supporting saidelectrode outside the envelope of said tube, a layer of di-electricmaterial covering a surface of said partition,.a metal plate spaced fromsaid partition by said di-electric material, a metallic casing enclosingsaid tube and divided by said partition electrically and mechanicallyinto two parts connected respectively to input and output electrodes ofsaid tube and secured respectively to said partition and said metalplate, each being provided with inlet-and outlet apertures for coolingfluid and means connected to said outlet apertures for passing a streamof cooling fluid through the parts of said casing to serve as a coolingmedium for said discharge tube. V

3. An electron discharge tube installation comprising a metal support,an electron discharge tube having an electrode extending outside thetube and secured to said support, an enclosing metallic casing securedto said support but spaced therefrom by dielectric material, andconnected electrically to a, further electrode of said tube to form apart of a circuit thereof, an outer containing housing having an upperwall or deck formed with an air inlet aperture and bearing said casingand electron discharge tube with at least part of said casing enclosedin said housing, means connected to said metallic casing for passing astream of air through said easing into contact'with a part of saidelectron discharge tube and means connected with the interior of saidhousing for passing a stream of air into said housing for cooling theexternal surface of said metallic casing.

4. An electron discharge tube installation comprising an electrondischarge tube having an electrode extending outside of the tube, ametal partition to which said electrode is secured, a metallic casingenclosing said discharge tube and divided by said partition into twoparts connected respectively to input and output electrodes of saidtube, one of said parts being secured to said partition and the otherbeing spaced therefrom by dielectric material, an outer containinghousing having an upper wall or deck formed with an air inlet apertureand bearing said casing and electron discharge tube with one part ofsaid metallic casing enclosed in said housing, means r connected to saidcasing for passing streams of air through the parts of said metalliccasing to cool said discharge tube and means connected with the interiorof said housing for passing a stream of air into said housing forcooling the external surface of the part of said metallic casing withinsaid housing;

5. An electron discharge tube installation comprising a metal support,an electron discharge tube having a plurality of electrodes including anelectrode extending outside the tube and secured to said support andprovided with heatradiating fins externally of said tube, a metalliccasing enclosing at least part of said tube and electrically connectedto a further electrode thereof, said casing being secured to saidsupport but electrically insulated therefrom, means for passing coolinfluid through said casing into.

contact with a part of said tube which is heated in operation, a housingenclosing said fins at least in part, and means for passing coolingfluid through said housing to abstract heat from said fins.

6. An electron discharge tube installation comprising a metal support,an electron discharge tube having a plurality of electrodes including anelectrode extending outside the tube and securedto said support andprovided with heat-radiating fins externally of the tube, a metalliccasing enclosing said tube and comprising two parts electricallyconnected respectively to input and output electrodes of said tube, oneof said parts being secured to said support and the other beingelectrically insulated therefrom, means for pass-- ing cooling fluidthrough said parts into contact with portions of said tube whichareheated in operation, a housing enclosing said fins at least in part,and means for passing cooling fluid through said housing to abstractheat from said 7. An electron-discharge tube installation comprising ametal support, an electron discharge tube having a plurality ofelectrodes including an electrode extending outside the tube and securedto'said support, a metallic casing enclosing- 8. An electron dischargetube installation comprising a metal support, an electron discharge tubehaving a plurality of electrodes including-an electrode extendingoutside the tube and secured to said support, a metallic casingenclosing said tube and comprising two parts electrically connectedrespectively to input and output electrodes of said tube, one of saidparts being secured to said support and the other part comprisingtelescoping sections one of which is electrically insulatedfrom saidsupport and the'other of which is con nected to a tube electrode to formpart of a shielded circuit of said tube, adjusting means for effectingrelative sliding of said telescoping parts to adjust the resonantfrequency of said shielded circuit, and, means for passing cooling fluidthrough said casing parts into contact with portions of said tube whichare heated in operation.

9. An electron discharge tube installation comprising a metal support,an electron discharge tube having a plurality of electrodes including anelectrode extending outside the tube and secured to said support, ametallic casing enclosing said conductors and slidably mounted in ,said'second casin part, adjusting mechanism for effecting sliding movement ofsaid member to adjust the resonant frequency of said input circuit,.

and means for passing cooling fluid through said casing parts intocontact with portions of said" tube which are heated in operation.

JOHN HENRY OWEN 'HARRIES.

